Academic literature on the topic 'Recouvrement vertical des nuages'

Abstract The apparent heat source Q1 and the apparent moisture sink Q2 are crucial parameters for precipitating systems studies because they allow for the evaluation of their contribution in water and energy transport and infer some of the mechanisms that are responsible for their evolution along their lifetime. In this paper, a new approach is proposed to estimate Q2 budgets from radar observations within precipitating areas at the scale of the measurements, that is, either convective scale or mesoscale, depending on the selected retrieval zone. This approach relies upon a new analysis of the radar reflectivity based on the concept of the traditional velocity–azimuth display (VAD) analysis. From the following five steps, Q2 is deduced from velocity and reflectivity fields: (i) mixing ratio retrieval using empirical relations, (ii) radial wind analysis using the VAD analysis, (iii) radar reflectivity analysis using a new analysis called reflectivity–azimuth display (RAD), (iv) retrieval of mixing ratio derivatives, and (v) Q2 retrieval. The originality and the main interest of the present approach with respect to previous studies rely on the fact it uses radar data alone and is based on a relatively low-cost analysis, allowing future systematic application on large datasets. In the present paper, this analysis is described and its robustness is evaluated and illustrated on three cases observed during the African Monsoon Multidisciplinary Analyses (AMMA) special observing period (SOP) field experiment (15 June–15 September) by means of the Recherche sur les Orages et Nuages par un Système Associé de Radars Doppler (RONSARD) radar. Results are analyzed in terms of the convective or stratiform character of observed precipitation.

Le site instrumenté Cézeaux-Aulnat Opme Puy de Dôme (CO-PDD) est une plateforme d'observation de l'atmosphère labellisée à l'échelle nationale par le CNRS et le Cnes, impliquée dans des réseaux internationaux pour le climat tels que GAW (Global Atmospheric Watch) et dans des infrastructures de recherche telles que Actris (Aerosol Cloud and Trace gases Research Infrastructure) ou Icos (Integrated Carbon Observation System). Composé de quatre stations de mesures in situ et par télédétection dans la région clermontoise, il produit sur le long terme des mesures de la composition atmosphérique gazeuse et particulaire, des nuages et des précipitations en incluant la dimension verticale. Sa localisation géographique lui permet d'échantillonner des masses d'air présentant des origines très diverses, dans des conditions d'ennuagement très fréquentes. Cela en fait un site exceptionnel pour caractériser la variabilité environnementale de la composition atmosphérique. The instrumented site Cézeaux-Aulnat Opme Puy de Dôme (COPDD) is an atmosphere observation platform labeled at the national level by CNRS and CNES institutes and involved in international climate networks such as GAW (Global Atmospheric Watch) and in research infrastructures such as ACTRIS (Aerosol Cloud and Trace gas Research Infrastructure) or ICOS (Integrated Carbon Observation System). Composed of four in situ and remote sensing measurement points around the city of Clermont-Ferrand, it produces long-term measurements of gaseous and aerosol atmospheric composition, clouds and precipitation, including the vertical dimension. Its geographical location allows various origin air masses to be sampled, in very frequent cloudy conditions. This makes it an exceptional site for characterizing the environmental variability of the atmospheric composition.

Abstract The International H2O Project (IHOP_2002) was designed to sample the three-dimensional time-varying moisture field to better understand convective processes. Numerous research and operational water vapor measuring systems and retrievals, via in situ and remote sensing techniques, were operated in the U.S. Southern Great Plains from 13 May to 25 June 2002. This was done in combination with more traditional observations of wind and temperature. Convection initiation (CI) sampling strategies were designed to optimally employ the array of ground-based and airborne sensors to observe the processes leading to the development of deep, moist convection. This case study examines several clear-air features and their impact on CI on 12 June 2002. The supercells that developed produced damaging winds and hail. The clear-air, preconvective features included (i) a mesoscale low pressure region, (ii) a dryline, (iii) an old outflow boundary, (iv) the intersection of (ii) and (iii), (v) internal gravity waves, and (vi) horizontal convective rolls. A unique combination of instruments was positioned to sample the preconvective environment on 12 June 2002. The Lidar pour l’Etude des Interactions Aérosols Nuages Dynamique Rayonnement et du Cycle de l’Eau (LEANDRE II) water vapor differential absorption lidar (DIAL), the airborne Electra Doppler Radar (ELDORA), and the Navy Research Laboratory (NRL) P3 aircraft in situ measurements provided information on the moisture and vertical velocity distribution within the boundary layer. Radiosondes, dropsondes, wind profilers, and an Atmospheric Emitted Radiance Interferometer (AERI) provided temperature, moisture, and wind profiling information. Although other ground-based sensors (i.e., S-band dual-polarization Doppler radar, Mobile Integrated Profiling System) were 50–150 km west of the CI area, they were useful for illustrating the boundary layer kinematics and reflectivity fields. Results suggest that the mesolow and mesoscale boundaries, respectively, acted to enhance the low-level moisture advection and convergence in the CI region. While internal gravity waves were present and appeared to modulate water vapor along the old outflow boundary, they did not play an obvious role in CI in this case. Horizontal convective rolls were observed beneath the new storms that initiated and may have helped to focus the CI in this case.

De nombreux logiciels du commerce proposent de créer des modélisations en 3D d'objets ou de scènes à partir uniquement de photographies. Cependant les professionnels, notamment les archéologues et les architectes, ont un certain nombre de contraintes qui restreignent fortement le choix du logiciel, telles que des ressources financières limitées, des connaissances peu approfondies en photogrammétrie et en informatique, des impératifs qui limitent le temps d'acquisition et de traitement, et enfin des attentes précises en terme de qualité, de précision et de complétude de la modélisation. Le laboratoire MATIS a développé un ensemble d'outils libres, open source, qui permettent d'effectuer l'ensemble des étapes du traitement d'un chantier photogrammétrique et qui fournissent des modèles 3D très denses et précis grâce à la rigueur de l'approche photogrammétrique ; ils représentent donc une solution intéressante pour ces professionnels du point de vue algorithmique.Cependant ils ont été développés pour des applications de recherche et sont donc peu ergonomiques pour le public non photogrammètre et non informaticien. C'est pourquoi une interface graphique est en cours de développement afin de fournir un accès simplifié et unifié à ces outils, notamment aux architectes et aux archéologues. Grâce à l'interface, l'utilisateur peut manipuler les images d'un même chantier et contrôler chaque étape du traitement qui comprend : le calcul automatique de points homologues entre les images, l'estimation des poses de la caméra et le calcul des modèles 3D. Les résultats peuvent être convertis en cartes de profondeur ombrées ou en nuages denses de points 3D (au format standard ply), et peuvent être affichés directement par l'interface. Pour offrir la possibilité de traiter des chantiers suffisamment variés, tout en masquant la complexité du paramétrage, la démarche retenue est de présenter à l'utilisateur un accès par grande famille de prises de vue, par exemple : chantier convergent, relevé de façades, chantier aérien sub-vertical, modélisation d'intérieur. . . Une attention particulière est apportée à la qualité de la documentation et à la portabilité du produit sur les principaux types d'ordinateur grand public (Linux, Mac et Windows). Cette interface, bien que non finalisée, permet déjà d'effectuer l'intégralité du traitement de chantiers de type convergent et est disponible en ligne. Des utilisateurs issus des différentes communautés de professionnels ciblées (archéologie, architecture, géologie, photogrammétrie architecturale) l'ont déjà testée et l'interface est régulièrement mise à jour afin de l'adapter aux remarques et demandes de ces testeurs.

Abstract. The radiative heating rate due to mineral dust over West Africa is investigated using the radiative code STREAMER, as well as remote sensing and in situ observations gathered during the African Monsoon Multidisciplinary Analysis Special Observing Period (AMMA SOP). We focus on two days (13 and 14 June 2006) of an intense and long lasting episode of dust being lifted in remote sources in Chad and Sudan and transported across West Africa in the African easterly jet region, during which airborne operations were conducted at the regional scale, from the southern fringes of the Sahara to the Gulf of Guinea. Profiles of heating rates are computed from airborne LEANDRE 2 (Lidar Embarqué pour l'étude de l'Atmosphère: Nuages Dynamique, Rayonnement et cycle de l'Eau) and space-borne CALIOP (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) lidar observations using two mineral dust model constrained by airborne in situ data and ground-based sunphotometer obtained during the campaign. Complementary spaceborne observations (from the Moderate-resolution Imaging Spectroradiometer-MODIS) and in-situ observations such as dropsondes are also used to take into account the infrared contribution of the water vapour. We investigate the variability of the heating rate on the vertical within a dust plume, as well as the contribution of both shortwave and longwave radiation to the heating rate and the radiative heating rate profiles of dust during daytime and nighttime. The sensitivity of the so-derived heating rate is also analyzed for some key variables for which the associated uncertainties may be large. During daytime, the warming associated with the presence of dust was found to be between 1.5 K day−1 and 4 K day−1, on average, depending on altitude and latitude. Strong warming (i.e. heating rates as high as 8 K day−1) was also observed locally in some limited part of the dust plumes. The uncertainty on the heating rate retrievals in the optically thickest part of the dust plume was estimated to be between 0.5 and 1.4 K day−1. During nighttime much smaller values of heating/cooling are retrieved (less than ±1 K day−1). Furthermore, cooling is observed as the result of the longwave forcing in the dust layer, while warming is observed below the dust layer, in the monsoon layer.

Abstract The detailed analysis of the three-dimensional structure of a dryline observed over the Oklahoma panhandle during the International H2O Project (IHOP_2002) on 11 June 2002 is presented. High-resolution observations obtained from the National Center for Atmospheric Research Electra Doppler Radar (ELDORA), S-band dual-polarization Doppler radar (S-Pol), water vapor differential absorption lidar (DIAL) Lidar pour l'Etude des Interactions Aérosols Nuages Dynamique Rayonnement et du Cycle de l'Eau (LEANDRE II; translated as Lidar for the Study of Aerosol–Cloud–Dynamics–Radiation Interactions and of the Water Cycle) as well as Learjet dropsondes are used to reveal the evolution of the dryline structure during late afternoon hours when the dryline was retreating to the northwest. The dryline reflectivity shows significant variability in the along-line direction. Dry air was observed to overrun the moist air in vertical cross sections similar to a density current. The updrafts associated with the dryline were 2–3 m s−1 and were able to initiate boundary-layer-based clouds along the dryline. The formation of this dryline was caused by high equivalent potential temperature air pushing northwestward toward a stationary front in the warm sector. Middle-level clouds with radar reflectivity greater than 18 dBZe near the dryline were detected by ELDORA. A roll boundary, which was associated with larger convergence and moisture content, was evident in the S-Pol data. It is found that the instability parameters most favorable for convection initiation were actually associated with the roll boundary, not the dryline. A storm was initiated near the roll boundary probably as a result of the combination of the favorable instability parameters and stronger upward forcing. It is noted that both the 11 June 2002 dryline and the roll boundary presented in this paper would not be identified if the special datasets from IHOP_2002 were not available. Although all model runs [fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5), Meso Eta, and Rapid Update Cycle (RUC)] suggested deep convection over the Oklahoma panhandle and several cloud lines were observed near the dryline, the dryline itself did not initiate any storms. The reasons why the dryline failed to produce any storm inside the IHOP_2002 intensive observation region are discussed. Both synoptic-scale and mesoscale conditions that were detrimental to convection initiation in this case are investigated in great detail.

Este estudo busca compreender quais eram as políticas de recursos humanos para estagiários e supervisores do setor de cobrança de um banco internacional e de que forma estas poderiam funcionar como fatores de estresse no trabalho. Trata-se de um estudo de caso, no qual se realizou a análise ergonômica do trabalho, com entrevistas, questionários, observações e análise documental. O estudo evidencia a presença de diversos fatores de estresse relacionados às políticas de RH para estagiários e supervisores. Há a falta de oportunidade de carreira para a maioria e desconhecimento dos critérios para efetivação, carreira e promoção. A mobilidade horizontal e vertical exige grande adaptação dos estagiários e impede a formação de vínculos, levando à necessidade de treinamentos constantes e suporte do supervisor. São admitidos funcionários jovens, que serão submetidos a uma carga de trabalho intensa. O treinamento é muito denso e teórico. A avaliação de desempenho estressa supervisores e estagiários, devido à sua inadequação quanto à sistemática e à forma. O sistema de premiação leva à busca de auto-superação e à competição pelos prêmios. Concluindo, considera-se que, na formulação das políticas de RH, deveriam ser considerados seus impactos na saúde dos trabalhadores a quem se destinam. Isso exigiria uma mudança de posicionamento da empresa com relação a crenças e valores referentes ao trabalhador, saúde, doença e poder. Palavras-chave: estresse no trabalho, políticas de recursos humanos, telemarketing, saúde mental, banco. HUMAN RESOURCES POLICIES AS STREESS FACTORS FOR THE WORK OF INTERNES AND SUPERVISORS IN THE COLLECTION SECTOR OF AN INTERNATIONAL BANK This study aims at understanding the human resources policies for interns and supervisors of the collection sector of an international bank and their role as factors of stress at work. This is a case study, where an ergonomic analysis of the work was made, with interviews, surveys, observations and documental analysis. The study shows the presence of given stress factors related to the human resources policies for interns and supervisors. Most of them experience lack of career opportunity and are not familiar with the criteria for them to become employees, as well as their careers and promotion possibilities. The horizontal and vertical mobility requires a major adaptation from the interns and hinders the formation of ties, giving origin to the need of ongoing training and support from the supervisor. The young employees who are hired will undergo an intense workload. The training is very dense and theoretical. The evaluation of the performance is a stress component for supervisors and interns, owing to their inadequacies as far as systematics and its form are concerned. The prize awarding system leads to the self-superation search and to competition for the prizes. Summing up, in the formulation of HR policies, their impacts on the health of the workers they are driven to should be taken into consideration. This would require a change of the behavior within the company regarding beliefs and values referring to worker, health and power. Key words: stress at labor, human resources policies, telemarketing, mental health, bank. LES POLITIQUES DE RESSOURCES HUMAINES COMME FACTEURS DE STRESS DANS LE TRAVAIL DES STAGIAIRES ET DES SUPERVISEURS DU SECTEUR DE RECOUVREMENT D’UNE BANQUE INTERNATIONALE Dans cette étude, on essaie de comprendre quelles sont les politiques de ressources humaines utilisées pour les stagiaires et superviseurs du secteur de recouvrement d’une banque inter-nationale et de quelle manière celles-ci fonctionnent comme facteur de stress dans le travail. Il s’agit d’une étude de cas dans laquelle une analyse ergonomi-que du travail a été effectuée, à partir d’entretiens, de questionnaires, d’observations et d’une analyse de documents. L’étude met en évidence la présence de divers facteurs de stress liés aux politiques des Ressources Humai-nes pour les stagiaires et les super-viseurs. Pour la plupart d’entre eux, l’opportunité de faire carrière n’existe pas et il y a un manque total de connaissance des critères établis pour intégrer l’effectif, avancer dans la carrière et obtenir une promotion. La mobilité, horizontale et verticale, exige une grande adaptation de la part des stagiaires et empêche que des liens se créent, provoquant ainsi un besoin de forma-tions constantes et de support d’un superviseur. On admet des fon-ctionnaires jeunes qui seront soumis à une charge de travail intense. La formation est très dense et théorique. L’évaluation des résultats stresse les superviseurs et les stagiaires, vu qu’ils sont inadéquats autant dans leur systématisation que dans leur forme. Le système de récompense provoque une recherche d’auto-dépassement et une compétition en vue des récompenses. Pour conclure, on estime que, lors de la formulation des politiques de Res-sources Humaines, leur impact sur la santé des travailleurs concernés devrait être pris en considération. Ceci impli-querait un changement de position de l’entreprise par rapport à ses certitudes et ses valeurs concernant le travailleur, la santé, la maladie et le pouvoir. Mots-clés: stress au travail, politiques des ressources humaines, telemar-keting, santé mentale, banque. Publicação Online do Caderno CRH: http://www.cadernocrh.ufba.br

Le transfert radiatif est crucial dans la modélisation de l’atmosphère, du climat, et pour la simulation du changement climatique. Les calculs de flux radiatifs au sommet de l’atmosphère et en surface permettent notamment d’estimer le bilan énergétique de la planète, grandeur dont la bonne estimation est une contrainte importante dans les simulations climatiques. De nombreux éléments interagissent avec le rayonnement dans l’atmosphère : gaz, aérosols, nuages, et différents types de surfaces (végétation, océans, neige...). Ces différents composants ne se comportent pas de la même façon avec le rayonnement solaire, dont la source est le soleil, et avec le rayonnement infrarouge, dont la source est la surface terrestre ainsi que l’atmosphère elle-même. Dans ces deux situations, les nuages, composés de gouttelettes d’eau liquide et/ou de cristaux d’eau solide, représentent une difficulté importante de modélisation. Les nuages sont des objets complexes, de part leur composition, leur géométrie, et leurs interactions multiples avec le rayonnement. L’interaction nuage-rayonnement est étudiée depuis de nombreuses années, et il a été démontré qu’elle représente un des obstacles les plus importants à l’amélioration des modèles globaux de simulation du climat. Dans cette thèse, nous nous intéressons à un des aspects clé dans la représentation de l’effet des nuages sur le rayonnement : le recouvrement vertical des nuages. Cette notion est en effet liée de manière directe à la couverture nuageuse, grandeur de premier ordre dans le calcul de l’albedo d’une scène nuageuse. Dans le cadre du recouvrement vertical des nuages, nous mettons en place un formalisme permettant d’explorer en profondeur différentes hypothèses de recouvrement des nuages, en particulier le recouvrement exponentiel-aléatoire. Nous montrons que cette hypothèse de recouvrement peut, sous certaines conditions, permettre une très bonne représentation des propriétés des nuages, à la fois géométriques et radiatives, même à partir d’un profil vertical nuageux de résolution grossière. Nous démontrons que la variabilité verticale sous-maille de la fraction nuageuse, bien que non prise en compte par les modèles atmosphériques grande échelle, peut avoir un impact significatif sur les flux solaires calculés au sommet de l’atmosphère. La prise en compte rigoureuse de la résolution verticale par le recouvrement est également un facteur important. Dans un second temps, nous incorporons ces résultats dans un code de transfert radiatif par Monte Carlo (RadForce). L’utilisation de ce nouvel algorithme, qui utilise par ailleurs une approche raie-par-raie pour les différents gaz atmosphériques, nous permet d’estimer l’altitude d’émission de chaque composant présent dans l’atmosphère. Ces nouveaux outils nous permettent d’analyser de manière nouvelle des forçages radiatifs liés aux gaz à effet de serre, ainsi que l’impact de la prise en compte du recouvrement vertical des nuages
Radiative transfer is a crucial process in atmospheric and climate modelling, as well as for climate change simulations. Computations of radiative fluxes at the top of the atmosphere and at the surface allow us to estimate the radaitive budget of the planet, which is very important to represent correctly when it comes to climate simulations. Many elements interact with the radiation in the atmosphere : gases, aerosols, clouds, and different types of surfaces (vegetation, oceans, snow...). These different components do not interact in the same way with solar radiation, that comes from the sun, and with infrared radiation, that comes from the earth’s surface and the atmosphere itself. In both situations, clouds, composed of liquid water droplets and/or solid water crystals, represent an important modeling difficulty. Clouds are complex objects, because of their composition, their geometry, and their multiple interactions with the radiation field. Cloud-radiation interaction has been studied for many years, and it has been shown that it represents one of the most important obstacles to the improvement of global climate models. In this work, we focus on one of the key aspects in the representation of the effect of clouds on radiation : vertical cloud overlap. This notion is indeed directly linked to the cloud cover, which is a quantity of first order importance in the calculation of the albedo of a cloud scene. Within the framework of the vertical cloud overlap, we develop a formalism allowing us to explore in depth various hypotheses of cloud overlap, in particular exponential-random overlap. We show that this overlap hypothesis can, under certain conditions, allow a very good representation of cloud properties, both geometric and radiative, even from a coarse resolution vertical cloud profile. We show that the vertical subgrid variability of the cloud fraction, although not taken into account by large-scale atmospheric models, can have a significant impact on the solar fluxes calculated at the top of the atmosphere. The rigorous consideration of vertical resolutions by the overlap is also an important factor. We then focus on incorporating these overlap results into a Monte Carlo radiative transfer code (RadForce). The use of this new algorithm, which also uses a line-by-line approach for the different atmospheric gases, allows us to model the emission altitudes of each atmospheric component. These new tools allow us to analyze in a new way the radiative forcings linked to greenhouse gases, as well as the impact of taking into account the vertical overlap of clouds and their vertical subgrid heterogeneity

Dans cette thèse on tente de réduire le biais “Too Few, Too Bright” partagé par la plupart des GCMs qui tendent à sous-estimer la couverture des nuages bas et à sur-estimer leur épaisseur optique. On travaille ainsi sur deux aspects de la représentation des nuages bas dans LMDz6. Sous-maille : On introduit une paramétrisation pour distinguer les fractions nuageuses volumiques CFvol et surfaciques CFsurf au sein des mailles du GCM, tout en recalibrant le calcul de l’eau condensée qc en prenant en compte l’épaisseur des mailles jusqu’alors négligée. Cette étape permet : -de diminuer l’épaisseur optique des nuages bas par la prise en compte de l’épaisseur des mailles dans le calcul de qc -d’augmenter la fraction nuageuse vue par le schéma de rayonnement qui reçoit CFsurf au lieu de CFvol Inter-maille : On propose une nouvelle paramétrisation de la longueur de décorrélation du schéma de recouvrement exponentiel-aléatoire, permettant d'évaluer la manière dont se recouvrent les nuages indépendamment dans chaque colonne atmosphérique, tout en prenant en compte le cisaillement de vent et en s’adaptant à des choix de modélisation comme la résolution verticale du GCM. On évalue les impacts radiatifs de ces paramétrisations avec le simulateur COSP2 dans lequel nous implémentons le cloud-generator du code radiatif ECRad. Sur nos diagnostiques, on observe : -une diminution des zones peu couvertes et très réfléchissantes -une augmentation des zones peu couvertes et peu réfléchissantes -une augmentation des zones à couverture et réflectance intermédiaire Ces nouvelles paramétrisations ont ainsi tendance à réduire le biais “Too Few, Too Bright” au dessus des océans tropicaux dans LMDz6
In this thesis we intent to reduce the "Too Few, Too Bright" bias shared by most GCMs, that tend to underestimate the low-cloud cover and overestimate its optical depth. We work on two aspects of the low-clouds representation in LMDz6. Sub-grid Scale: We introduce a parametrisation to distinguish cloud fractions by volume CFvol and by surface CFsurf inside GCM grid boxes, and we recalibrate the calculation of condensed water by taking into account the depth of the grid boxes that use to be neglected. This step allows: -to reduce the optical depth of clouds by taking into account the depth of grid boxes in the calculation of qc -to increase the cloud fraction seen by the radiation scheme, that receive CFsurf instead of CFvol Inter-grid Scale: We propose a new parametrisation of the decorrelation length of the exponential-random overlap scheme, that allows evaluating the overlap of clouds independently in each atmospheric column, while taking into account wind shear and being adaptive to modelling choices such as the vertical resolution of the GCM. We evaluate the radiative impacts of these parametrisations with the COSP2 simulator package in which we implement the cloud-generator of the radiative code ECRad. Our diagnostics show: -a reduction of the low-covered and highly-reflective areas -an increase of the low-covered and low-reflective areas -and increase of the mid-covered and mid-reflective areas These new parametrisations then tend to reduce the "Too Few, Too Bright" bias over tropical ocean in LMDz6

The European project BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) focuses on aerosol-cloud interactions. Vertical wind velocities near cloud base, and cloud condensation nuclei (CCN) spectra, are the two most important input parameters for aerosol-cloud parcel models in determining cloud microphysical and optical properties. Therefore, the present study focuses on the instrumental development for vertical wind measurements to improve aerosol-cloud closure studies. Enhancements in Remotely Piloted Aircraft Systems (RPAS) have demonstrated their potential as tools in atmospheric research to study the boundary layer dynamics, aerosols and clouds. However, as a relatively new tool for atmospheric research, RPA require instrumental development and validation to address current observational needs. A 5-hole probe is implemented on a remotely piloted aircraft (RPA) platform, with an inertial navigation system (INS) to obtain atmospheric wind vectors. The 5- hole probe is first calibrated in a wind tunnel (at Météo-France, Toulouse, France), and an error analysis is conducted on the vertical wind measurement. Atmospheric wind vectors obtained from RPA flights are compared with wind vectors determined from sonic anemometers located at different levels on a 60 m meteorological mast (Centre de Recherches Atmosphériques, Lannemezan, France). Good agreements between vertical wind velocity probability density functions are obtained. The power spectral density of the three wind components follow the -5/3 line for the established regime of turbulence (Kolmogorov law). Turbulent kinetic energy (TKE) values calculated from the RPA are somewhat higher than TKE compared to the sonic anemometer; however, the results agree with those reported in other experiments that compare RPA platforms and sonic anemometers (Lampert et al. (2016), Båserud et al. (2016)). As the RPA equipped with a 5-hole probe (defined as the ``wind-RPA'') is developed for aerosol-cloud observations, updraft velocities near cloud base are compared with cloud radar data during a BACCHUS field campaign (Mace Head Research Station, Ireland). Three case studies illustrate the similarity of in-cloud updrafts measured between the wind-RPA and the cloud radar. A good agreement between vertical velocities of both instruments over a range of different meteorological conditions is found. Updraft velocity measurements from the wind-RPA are implemented in the aerosol-cloud parcel model to conduct a closure study for stratocumulus case with convection sampled during a BACCHUS field campaign in Cyprus. Aerosol size distributions and CCN were measured at a ground-site, which served as input to the aerosol-cloud parcel model along with the updraft velocities at cloud base measured by the RPA. In addition, the RPA conducted a vertical profile through the cloud layer and measured the shortwave transmission of solar irradiance during the ascent. The aerosol-cloud parcel model also shows that entrainment has a greater impact on cloud optical properties than variability in updraft velocity and aerosol particle concentration. Results of the case study for the Cyprus field experiment are consistent with results for similar closure studies conducted during the Mace Head field campaign (Sanchez et al., 2017), and reinforce the significance of including entrainment processes in cloud models to reduce uncertainties in aerosol-cloud interactions.

Au cours de la dernière décennie, le cloud computing est devenu l’environnement standard de déploiement pour la plupart des applications distribuées. Alors que les fournisseurs de cloud ont étendu de manière continue leur couverture géographique, la distance entre leurs centres de données et les utilisateurs finaux se traduit toujours par une latence et une utilisation du réseau importantes. Avec l'avènement de nouvelles familles d'applications telles que la réalité virtuelle / augmentée ou les véhicules autonomes, nécessitant de très faibles latences, ou l'IoT, qui génère d'énormes quantités de données, l'infrastructure centralisée des clouds s’avère incapable de supporter leurs exigences. Cette situation a mené à l’expérimentation de nouvelles alternatives plus distribuées telles que le fog computing. Bien que les prémisses de cette infrastructure semblent prometteuses, une plate-forme de type fog n’a pas encore été créée. Par conséquent, une attention particulière doit être consacrée à la définition des contraintes appropriées de conception qui permettront de réaliser pleinement ces objectifs. Dans cette thèse, nous visons à concevoir des blocs de construction pouvant fournir des fonctionnalités de base pour la gestion d’une infrastructure de type fog. En partant du principe de préservation de la localité intrinsèque au fog, nous concevons un réseau de recouvrement paresseux et tenant compte de la localité, appelé Koala, qui permet une gestion décentralisée efficace sans créer de surcharge de trafic lié à la maintenance du réseau. Afin de capturer des exigences supplémentaires provenant de la couche applicative, nous avons étudié le déploiement d’une application fondée sur une architecture à base de microservices, à savoir Sharelatex, dans un environnement fog. Nous examinons comment ses performances en sont affectées et quelles fonctionnalités la couche de gestion peut fournir afin de faciliter son déploiement dans le fog et améliorer ses performances. En se fondant sur les blocs de bases définis et sur les exigences extraites du déploiement de l'application dans le fog, nous concevons un mécanisme de découverte de service qui répond à ces exigences et intègre ces composants dans un seul prototype. Ce prototype permet une évaluation complète de ces composants sur la base de scénarios dans des conditions réelles
In the last decade, cloud computing has grown to become the standard deployment environment for most distributed applications. While cloud providers have continuously extended their coverage to different locations worldwide, the distance of their datacenters to the end users still often translates into significant latency and network utilization. With the advent of new families of applications such as virtual/augmented reality and self-driving vehicles, which operate on very low latency, or the IoT, which generates enormous amounts of data, the current centralized cloud infrastructure has shown to be unable to support their stringent requirements. This has shifted the focus to more distributed alternatives such as fog computing. Although the premises of such infrastructure seem auspicious, a standard fog management platform is yet to emerge. Consequently, significant attention is dedicated to capturing the right design requirements for delivering those premises. In this dissertation, we aim at designing building blocks which can provide basic functionalities for fog management tasks. Starting from the basic fog principle of preserving locality, we design a lazy and locality-aware overlay network called Koala, which provides efficient decentralized management without introducing additional traffic overhead. In order to capture additional requirements which originate from the application layer, we port a well-known microservice-based application, namely Sharelatex, to a fog environment. We examine how its performance is affected and what functionalities the management layer can provide in order to facilitate its fog deployment and improve its performance. Based on our overlay building block and the requirements retrieved from the fog deployment of the application, we design a service discovery mechanism which satisfies those requirements and integrates these components into a single prototype. This full stack prototype enables a complete end-to-end evaluation of these components based on real use case scenarios